4C20.60 - Heat of Crystallization

Code Number:
Demo Title:
Heat of Crystallization
Change of State
Area of Study:
Heat & Fluids
Re-HeaterTM Portable Heat Packs Containing Sodium Acetate.

The heat packs have an activating button.  Gently push on the button and the solution of sodium acetate will start to change to a solid.  As it does so it releases heat.

  • B. Sandnes, "The Physics and the Chemistry of the Heat Pad", AJP, Vol. 76, #6, June 2008, p. 546.
  • Narayanan Menon, "A Simple Demonstration of a Metastable State", AJP, Vol. 67, #12, Dec. 1999, p. 1109. 
  • Sophie Bushwick, "Conquer Cold With DIY Hand Warmers", Popular Science, Vol. 286, #6, Dec. 2014, p. 79.
  • Theodore Gray, "Icy Hot", Popular Science, Vol. 279, #5, Oct. 2007, p. 80. 
  • Cy Tymony, "Cheap Gel Packs for Swollen Muscles", Sneaky Uses for Everyday Things, p. 7.
  • "Heat Packs. Item # 3227 Series Suggested Lesson Plans for Elementary, Middle, and High School", American Scientific.
  • Borislaw Bilash II, “Heat Me Up With Heat of Crystallization“, A Demo A Day – A Year of Physical Science Demonstrations, p. 63.
  • Borislaw Bilash II, “Crystal Heat Pack“, A Demo A Day – A Year of Physical Science Demonstrations, p. 170.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.